i have some broccolli plants which are infested with caterpillars (cabbage whites) as the broccolli have now finished flowering, should i let them complete there life cycle or should i spray them and kill them off thanks in anticipation
It's amazing how much caterpillar damage some plants can take without coming to serious harm. You will have to use your judgement.
If the plants are still growing OK, leave the caterpillars & pat yourself on the back for being organic.
But if the plants are suffering, pick off and dispose of all the caterpillars you can see and pat yourself on the back for not using an insecticide.
Whatever you decide please don't use a spray.